The invention relates generally to an x-ray shielding system for automated digital radiographic inspection and, more particularly, to an x-ray shielding system for automated digital radiographic inspection of aircraft components.
Aircraft components, such as aircraft fuselage frames, are repeatedly inspected during the life of an aircraft, to detect potentially damaging defects. Presently, aircraft fuselage frames are inspected visually, which requires that the insulation first be removed from the frame. The exposed fuselage frame is then examined visually, with mirrors being used to inspect portions that are difficult to access. However, visual inspection has several drawbacks. First, only large cracks (at least 5 cm in length) are reliably seen, whereas it would be desirable to detect cracks as small as about 1 cm in length. Second, it is difficult to quantify and record the cracks that are visually detected. Third, visual crack inspection is subject to an inspector fatigue factor. Fourth, improper reinstallation of the insulation can introduce moisture condensation, which can lead to corrosion. Moreover, this procedure is time and labor intensive, with a typical inspection period of about five-person days for commercial aircraft, in addition to the labor required to disassemble and reassemble the aircraft interior.
X-ray imaging provides a useful tool for avoiding many of the problems associated with the visual inspection of fuselage frames. Presently, certain areas of the fuselage are examined using x-ray film, and an x-ray source is placed in the fuselage to expose the film. This x-ray imaging method is potentially advantageous relative to visual inspection, in that the insulation need not be removed, small cracks (on the order of 1 cm in length) can be detected, the inspector fatigue factor is eliminated, and the inspection time is reduced. However, due to the large size of aircraft components, powerful x-ray sources are employed, for example on the order of one to one hundred Rad per minute (1-100 R/min). Safety considerations usually dictate that the area around the aircraft be cleared of personnel while x-ray inspections are performed, preventing the concurrent performance of other maintenance activities. In addition, the use of x-ray film is cumbersome, producing x-ray images that are difficult to store and to systematically analyze.
Accordingly, it would be desirable to employ digital radiography to image the aircraft fuselage and other aircraft components. Advantageously, this would provide x-ray images that are conveniently stored and analyzed in digital form. However, digital radiography is subject to the radiation exposure concerns discussed above. In addition, digital radiography necessitates moving the x-ray source and an x-ray detector around the aircraft component to image the large components. This, in turn, would require repeated operator intervention. Accordingly, it would be desirable to provide a shielded digital radiographic inspection system for imaging aircraft components that provides additional protections against exposure to harmful radiation.
Briefly, in accordance with one embodiment of the present invention, an x-ray shielding system includes a beam controller configured to surround an x-ray source. The beam controller includes a source shield and an aperture. The x-ray shielding system further includes a detector shield configured to position behind an x-ray detector. The source shield and the detector shield are adapted to block x-rays, and the aperture is adapted to transmit x-rays.
In accordance with another embodiment, a shielded digital radiographic inspection system includes the x-ray source and the beam controller surrounding the x-ray source. The beam controller includes the source shield and the aperture. The beam controller is configured to rotate the aperture around the x-ray source. The inspection system further includes a digital x-ray detector positioned radially outward from the x-ray source and facing the aperture. The digital x-ray detector is configured to be movable along an orbit around the x-ray source. The inspection system further includes the detector shield configured to be movable with the digital x-ray detector and positioned behind the digital x-ray detector.
In accordance with a method embodiment, a shielded digital radiographic inspection method for imaging an aircraft component includes surrounding the x-ray source with the beam controller to produce a collimated x-ray beam through the aperture of the beam controller. The method further includes shielding a back side of a digital x-ray detector to reduce x-ray flux behind the digital x-ray detector, the digital x-ray detector being positioned radially outward from the x-ray source, outside the aircraft component, and facing the aperture. The method further includes imaging a portion of the aircraft component. The imaging includes activating the x-ray source and collecting an image with the digital x-ray detector. The method also includes rotating the aperture around the x-ray source to a subsequent aperture orientation and moving the digital x-ray detector along an orbit around the x-ray source to a subsequent detector position facing the aperture. The rotation of the aperture, the motion of the digital x-ray detector, and the imaging are repeated for a plurality of aperture orientations and detector positions to obtain a plurality of images of an annular portion of the aircraft component.